This is a new release based on the Gecko 15.0 code base with additional branch development. It incorporates many changes under the hood that go far beyond the scope of this document.

A few highlights, in addition to security fixes:

Performance improvements for the rendering engine
More HTML 5 implemented
Better handling of memory, resulting in smoother operation of the browser
More responsive user interface when the browser is busy
Prevention of memory leaks through add-ons
Better implementation of the Quickdial page
Localization of Pale Moon specific preferences and options (work in progress)
Reinstatement of the previous user interface, keeping it in line with version 12 (Firefox 15 has UI changes that makes the controls flat, monochrome and borderless, which isn't desired for Pale Moon)
The padlock has returned for secure pages! It can be found in front of the URL when you browse to a secure page, with optionally company information if supplied by the server

Some things new to the Firefox code base that are excluded or disabled by default:

Built-in PDF reader in javascript - use a standalone, dedicated reader
(this is both a security and functionality consideration)
Additional advanced web development tools - the average user never needs these
Web apps on the desktop - Pale Moon is a browser, not a pseudo-OS
Windows Metro UI

Pale Moon will be released independent of Mozilla Firefox, as it will take time to build and test based on release code, and add Pale Moon specific enhancements; the Mozilla release schedule is not followed. Pale Moon is an independent development based on Firefox, but will not follow Firefox to the letter. This is still a project run in free time and without commercial incentives, and testing the browser on at least a few systems before releasing it to the public is an important step in releasing a browser that is stable enough for public, daily use. Because Firefox shares its source code over several different platforms, patches that are implemented for a new version quite regularly do not apply to Windows browser builds and are therefore irrelevant to Pale Moon development. Pale Moon will be updated only for select and relevant updates of the Firefox base source code and otherwise develop independently on the chosen version of the Gecko engine.
This also means that Pale Moon will not be built based on beta, release candidate, milestone, or other development releases of the Firefox source code (there will not be any Pale Moon "nightly", "aurora" or "beta" builds available to the public). Only relevant "Release" source code will be used to ensure stability.

PaleMoon was supposed not to rely on Firefox builds... and yet it predates FF...

Click to expand...

I checked out Pale Moon's forum yesterday and saw the announcement by Moonchild that v 15.0 would be released today. Normally he released the next update/version a week or so after Firefox's release. In the past Moonchild skipped some though or omitted some code. What I like in Pale Moon is that there are no silent updates.

Firefox-variant Pale Moon 15.1 for Windows has been released, promising to resolve a “fairly large number of issues with the initial version”. Version 15.1, also available as a dedicated 64-bit build, includes fixes for the mouse wheel scrolling preferences, memory inflation while playing some canvas games and a fix for private browsing mode.

This is a minor update to address some important performance (high CPU usage) and stability (browser hang) issues in Pale Moon 15.1. Specifically, some of Tete009's patches were backed out.
Azure acceleration with his patches is still in place, but the multi-threaded box blur and cairo patches were removed to fix the CPU and browser hang issues, respectively.